Field of the Invention
The invention relates to a plate-type heat exchanger, particularly for motor vehicles, with a plurality of plate groups to form first and second and/or third flow paths, whereby a spatial region for the fourth flow paths is formed between adjacent plate groups.
Description of the Background Art
Heat exchangers are provided in motor vehicles in a wide variety and for a multitude of different purposes. Thus, evaporators are used in climate control systems in order to cool the air by evaporation of the refrigerant in flow paths flowing through the evaporator, in order to bring about an air conditioning and dehumidification in the vehicle interior. Flat tube-type or plate-type evaporators have become known for this purpose.
In regard to motor vehicles, the main trend in recent times has been to reduce the fuel consumption of a motor vehicle and the CO2 emissions associated therewith. This is also achieved in the case of motor vehicles with an internal combustion engine in that during temporary idling caused by stopping of the vehicle at a traffic light or in similar situations, for example, the vehicle's combustion engine is turned off. As soon as the vehicle is reactivated to drive by actuation of the gas pedal or the clutch pedal, the internal combustion engine is automatically restarted. This technology is also called the start-stop method. Such start-stop methods have already been implemented in low-consumption motor vehicles. For commercially available vehicle climate control systems with a cooling circuit according to the vapor compression cycle, the compressor of the cooling circuit is usually powered by a belt drive, driven by the vehicle's driving engine. When the engine is idle, i.e., when the compressor drive is not working, the climate control system can no longer be described as cold-producing. With a turned-off engine in the start-stop operation, the air conditioning of the motor vehicle can therefore no longer operate and provide a cooling capacity for cooling the vehicle's interior. As a consequence of this situation, the evaporator of the climate control system warms up relatively quickly and the air flowing through the evaporator is cooled only slightly or too little. For one thing this causes the interior vehicle temperature to rise and to affect the physical comfort of the vehicle passengers negatively.
Apart from the temperature reduction, a dehumidifying process also occurs in a vehicle climate control system, because the moisture in the air condenses in the evaporator and leaves the vehicle through a condensate outlet. The air flowing through the evaporator is therefore dehumidified and enters dehumidified the motor vehicle interior. In the case of the active start-stop operation, the dehumidification of the air entering the vehicle interior can thus no longer be sufficiently assured, so that the humidity in the vehicle interior increases during the active start-stop operation. This also results in an increase in humidity which is perceived as unpleasant and uncomfortable by the vehicle passengers.
In order to prevent or slow down these temperature- and humidity-increasing processes, the so-called storage evaporator was developed which, in addition to the actual evaporator function, also comprises a cold storage medium that removes heat from the air flowing through the evaporator in an active start-stop operation and continues to cool and dehumidify it.
These storage evaporators have been disclosed, for example, in DE 102006028017, which corresponds to U.S. Pat. No. 8,495,894, and which is incorporated herein by reference. The storage evaporator disclosed has two separate heat exchanger blocks, the evaporator and the storage section, which are produced in different production processes and are connected together just before the soldering process and are then soldered together to a unit. The main evaporator has two flat tube rows, arranged one behind the other in the air flow direction, and the storage section is connected downstream of these two flat tube rows in the air flow direction. The storage part has double-tube rows with two tubes being inserted into one another, whereby the refrigerant flows in the interior of the inner tube and the cold storage medium is disposed in the space between the outer tube and the inner tube.
However, in the conventional art, the corresponding production process is very complex and expensive, because many different parts have to be matched, joined, and calibrated in order to be able to produce a properly functioning heat exchanger. In particular, a double tube with covered tube entries proves to be relatively complex, the number of parts is very high with at the same time a high number of different parts and compliance with tolerances represents a risk for process capability due to the many structural parts. This in turn means an increased risk of leakage, so that apart from the parts costs the risk of the reject rates also increases.